Charging Alarm

[Sailorjack]

Hi All

I launched today and she floated.

After I ran the engine for about 7-10 mins I started to get an alarm from the engine panel. The charging light was coming and the alarm was sounding on for about two seconds. Then it would go silent for about 15 seconds or so. I did notice that the voltage was dropping from 14.5 volts to about 14.0 volts. I haven't made any changes over the winter. I would appreciate your advice.

 

[Mike 1]

May seem simple, check your belt tension. When I got my boat I checked mine, it was a bit slack snugged it and after it ran for a bit would loosen. Turned out the Alternator mount was on wrong. fixed that, never had a problem since. Again, that would be the simple, best case...which it NEVER is!

 

[Jim Legere]

If its not belt tension and you have checked the wiring and cleaned contacts, its probably worth getting the alternator off and into a good auto-electric shop for a look. Could be brushes or the voltage regulator. The original alternators were Hitachi, so any good shop should be able to help. If you need a replacement, check out Spyder Marine in FL (google them - I haven't bought from them but their prices look better than most).

Glad to hear sailing season has arrived on the Rock!

 

[Bill Roosa]

If you are seeing 14 ish volts then the alternator is OK. The regulator probably needs a looking at though. It controls the voltage. I suspect that it is turning the alt on (14.4) then "crapping out" for some reason and the batt voltage is falling to 14 volts when it does. The batts will take some time to drift down to their resting voltage so 14 is pretty believable just after having the alternator on. The regulator should never turn the alternator OFF. It should at least be trickle charging the batts.
The way to test is to measure the rotor voltage when the alarm is on. The rotor is the spinning part and the regulator should be supplying some (probably a lot less than batt voltage but not 0 volts) to it. The problem is if it is an internal regulator as there is no direct way to actually get a test probe to the right wires. If the regulator is external then the pigtail that connects to the alternator rear like a phone jack (square plastic connector with two wires) is the place to use your test probes. One wire will ether be missing (but there will be a terminal on the alternator side) or go to the tach. the other is the rotor field current wire and that is the one you want to test. + probe to that wire and - probe to the alternator case.
Good luck

 

[Sailorjack]

Thanks for the responses.
Mike the belt was loose but tightening did not solve the problem. I had the alternator rebuilt about 2 years ago and have not put many hours on the engine since. I may have to do as Jim suggested and take it to a auto shop to have it tested. I did notice today when I ran the engine the alarm condition happens only when the RPMs are below 1000. If I run the engine over 1000 RPMs the alarm stops. If anyone has any more ideas I'm listening.
Thanks

P.S. Jim, the boat may be in the water but with current daytime temperatures of about 6 or 7 degrees C sailing season has not started yet, but hopefully soon.